Like the Reese's Peanut Butter cup before it, the Amazon Kindle app on Windows Phone is two great tastes--or in this case, platforms--that go together. I'm enthusiastic about all the app picks I've made so far, of course. But I've never been this enthusiastic. Kindle on Windows Phone is a milestone, one that all Windows Phone owners should avail themselves of. So it's another app of the week, sure. But it's also one of the top apps ever released for Microsoft's new smart phone platform.

I've been advocating the superior Amazon Kindle device to readers since the day the company announced the first version, way back in 2007. The problem at the time was that the first (and second) generation Kindle device was simple too expensive, like the typical Apple product.

But two trends emerged since then, making the Kindle a no-excuses no-brainer. First, prices continued dropping, and today's ultra-thin and ultra-light Kindle 3 costs just $139, while still providing the superior reading experience, both on Kindle-like dedicated devices and wanna-be readers like the iPad. Second, Amazon evolved Kindle into a true platform, making this superior reading experience available to customers on their device of choice. As I write this, there are wonderful Kindle apps available for Windows, the Mac, iPhone/iPod touch, iPad, Blackberry, and Google Android in addition to Windows Phone and, soon, web browsers.

Kindle isn't a platform just because you can read books on different devices. It's a platform because you can do so intelligently. Let's say you're reading the latest James Patterson thriller on your Kindle device and, as with any book, at some point you stop reading to move on to other things. Then you're standing in line at the grocery store or airport, or it's a lull during your kid's baseball game, and you think, I'd really like to pick up reading where I left off, but you forgot the device. Well, no problem: You can simply open the book on your Kindle app (on whatever mobile platform) and that's exactly what happens. You read a bit, and then later when you pick up again on the actual device, you're right where you left off again.

This automatic synchronization--not just of last page read, but also of notes and highlights--is only one of the things that makes Kindle special, and of course other platforms are ripping off this feature. But the reason it's more compelling with Kindle than, say, Apple's lock-in iOS-based devices (with iBooks) is because of sheer choice you get with devices.

That choice extends, too, to the bookstore. Amazon's bookstore for Kindle features more books--and here I mean real books, not the out-of-print freebies that Google and others pad their numbers with--and generally lower prices than the competition. (Though Apple has raised prices somewhat for all eBook platforms, as I've noted elsewhere. At least their own bookstore, iBooks, hasn't taken off.) I'm talking over 775,000 actual books, over 95 percent of all New York Times best-sellers, hundreds of first-rate newspapers and magazines, blogs, and of course a ton of free books as well.

And then there's the Windows Phone app. Aside from the basics--it provides the same book sync, sharing, rotating viewing, and mobile web-based shopping experiences as other smart phone Kindle apps, of course. But because it's a Windows Phone app, it also features superior typography and design, thanks to its use of the Metro design principles, and excellent text rendering when reading.

(In side-by-side tests with the iPod touch 4G's higher resolution display, I found the Kindle app on both platforms to display text almost identically. What puts Windows Phone over the top, of course, is the actual UI, which is just prettier and easier to use on Microsoft's platform. That Windows Phone devices have a bigger screen is, of course, just an added benefit.)

In any event, Kindle on Windows Phone is a no-brainer, and as with last week's pick, it's one of only two third-party apps that can be found on my own phone's home screen. In fact, Kindle is so good, it's not just on the home screen, it's on the top row of the home screen. I love it, and if you care about reading at all, so will you.